Ruminant, a grazing animal that chews a cud and has split hooves. Ruminants include domestic cattle, bison, buffaloes, camels and llamas, giraffes, deer, pronghorns, antelopes, sheep, and goats. These animals, except camels and llamas, have no upper front teeth; in place of teeth there is hardened gum, against which the lower front teeth bite. Ruminants hastily bite off and swallow their food (chiefly grasses, herbs, and twigs). They then lie down or stand at rest and chew the cuds.
In most ruminants, the stomach has four parts, or chambers. The more solid food passes to the first chamber (the paunch, or rumen), where it is stored. The rumen gradually passes it to the second compartment (the honeycomb bag, or reticulum). Here microorganisms begin to break down the food; it is formed into ball-like masses (boluses, or cuds). When the animal is at rest these pass back up the esophagus to the mouth, where they are thoroughly chewed and mixed with saliva, which aids in further digestion. The food is again swallowed and passes to the third chamber (the psalterium, or omasum). It then passes into the fourth chamber (the abomasum) and is mixed with gastric juices; here the stomach's part of digestion is completed.
Ruminants form the suborder Ruminantia of the mammalian order Artiodactyla.